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Road Bike Tires: What to Know

Adam Kavanagh
March 09, 2017

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A lot attention is given to a bike's frame, weight, and composition but the little over two centimeters of tread keeping us connected to the road often gets overlooked. Choosing the right tires can do wonders for your riding experience. Good tires can improve comfort, traction and lower rolling resistance for a faster, more efficient ride. They can also be highly durable, lasting for months at a time without a puncture. To help you know what to look for when choosing a tire, we've created this comprehensive guide of what to know about road bike tires.

Tire types

There are three types of road bike tires that are commonly used, a 'clincher' tire is the one we are most familiar with. If you follow professional cycling, you'll notice almost all riders prefer 'tubular' tires, and taking a lead from mountain biking, 'tubeless' tires have started to make their way into the road scene. Below is a description of each.

Clincher: These tires are the most common type and are currently sold with almost every new bike. Clincher tires require a tube, which, sits in between the wheel rim and the tire to inflate and hold air. In the event of a puncture, this inner tube can easily be replaced or patched. Clincher tires feature a steel (aka: wire) or kevler fiber bead (aka: folding) on their side, which hooks underneath the ridges of a wheel rim to hold the tire in place.

Tubular: These tires are popular with professional riders for the performance benefits they provide, but less popular with recreational riders due to their lack of everyday functionality. Tubular tires still utilize an inner tube but it is sewn into the tire rather than sitting separately from it like a clincher, as a result, tubulars need to be stuck to the wheel via glue or special tape. A benefit of sticking the tire to the rim is that in the event of a flat, the tire will stay on the rim, and you can continue to ride without losing control.

Tubular wheels are able to save some weight over clincher and tubeless wheels by not requiring the ridges for the tubeless and clincher tire beads to hook onto, and their rolling resistance is said to be better too. Anecdotally, tubulars are also said to feel more supple and provide a better ride quality. On the flip side, changing a flat is tough work, you can't simply swap out a new tube like you would with a clincher, it requires another pre-glued tubular tire, which, is difficult to carry. And if your tubular tire has been glued correctly, it will be extremely difficult to take off with your hands alone. Lastly, tubular tires are the most expensive option, which another reason for why they're considered a race-day item.

Tubeless: This technology has long been used in the mountain biking and cyclocross realms and is beginning to grow in popularity on the road too. As the name suggests, there is literally no tube with tubeless tires, instead, it is just a tire that hooks onto the wheel as a normal clincher would, but with much tighter tolerances to create a firmer, airtight seal. Sealant is then added into the tire to plug small holes and splits, reducing the chance of flats. In addition to a reduction in flats, tubeless tires provide better rolling resistance than clinchers and can be run at lower pressures, improving traction, comfort and control. In order to use tubeless tires, you'll need compatible wheels.

Anatomy of a tire

There are a number of elements that make up a standard tire that are worth knowing as each will affect performance, comfort, and durability.

Bead: The tire's bead holds the tire onto the rim and is only applicable for clincher and tubeless tires. The bead is typically made from either wire or kevlar, wire featuring on inexpensive tires, kevlar featuring on more premium options. Clincher tires with kevlar beads are also referred to as 'folding' tires.

Casing: The casing is the foundation of the tire, connecting the beads to one another and providing enough resistance from stretch to keep the air in while conforming to the ground surface. The casing is made from either nylon, cotton or silk and measured in 'threads per inch' or 'TPI'. Tires with a lower TPI count (e.g: 60 TPI) provide good puncture protection but poor rolling resistance, conversely, tires with high TPI counts (120 TPI +) provide a more supple ride with good rolling resistance but often with reduced puncture protection.

Puncture protection: In order to improve their resistance to punctures many tires will add a 'sub-tread' layer or 'puncture proof belt'. Some tires will simply feature more rubber, increasing the thickness of the tread, while others will use specific compounds to enhance their resilience. Sub-layers increase a tire's rolling resistance and add weight, and so it is a balancing act for manufacturers to create a fast, lightweight tire that can offer good levels of puncture protection. Some sturdier tires designed for winter training and commuting will feature puncture protection in the sidewall too.

Sidewall: This is literally the side of the tire, and is part of the casing that isn't intended to touch the ground, as a consequence this part of the tire is the thinnest. Important details such as the wheel and tire size, and recommended tire pressure will be found on the sidewall.

Tread: Tread is the part of the tire that contacts the ground and will be made from varying compounds with different tread patterns depending on it's intended use.

Tire size

Tire and wheel sizes for road riding don't vary as much as mountain biking with a 700c wheelsize almost universal for road riding, and tire sizes typically ranging from 22mm to 28mm. Despite the relatively consistent size options, it's important to know what different tire sizes mean in terms of performance, comfort, and durability.

Wheel and tire sizes are governed by an international standard known as 'ISO 5775', a standard designed to make information clear and consistent. The system uses two numbers to detail the wheel and tire size. The first number refers to the rim diameter in millimeters, in most cases, this figure is '700c'. The second number refers to the tire diameter in millimeters, in most cases, this ranges from 23mm to 28mm for road tires but can be upwards of 35mm for cyclocross and recreational use tires. So a typical road wheel with a 25mm tire will be represented as 700c x 25mm.

Previously the standard used was the 'ETRTO' or European Tyre and Rim Technical Organisation', and their markings looked more like this; 37-622. The first number refers to the width of the tire, and the second number refers inner diameter of the tire. And finally there is also inch markings, which look like this; 28 x 1.40". In this case, the first number refers to the outer diameter of the rim and the second number refers to the tire width.

The trend in recent times has been towards larger tires that provide better comfort and traction, whilst providing reduced rolling resistance at the same time. In the past, it was thought that skinnier tires, pumped up to high pressures were faster, but the latest research suggests bigger and softer is better. Wider tires can be run at lower pressures providing a more supple ride and also conform better to the road surface and provide additional comfort. Another benefit of larger tires is the shorter and wider contact patch, which, leads to less resistance and sidewall deformation, resulting in a faster tire. Specialized conducted their own studies into tire width and resistance, finding that there was almost a 25% reduction of resistance when using a 28c tire compared to a 21c tire. Read our review of the Specialized Turbo tires for more information and insight into tire widths.

Before you go buying the largest road tire available, it's important to know that the tire's width must sit within the recommended wheel rim range and not be compromised by frame clearance, brakes or any additional accessories such as fenders. Consult your place of purchase if you're unsure of the limits of your bike.

The importance of the wheel to a tire

We've discussed the influence tire size has on performance and comfort but the choice of wheels is just as important.

Modern wheels are becoming wider, not only to accommodate the push for larger tires but to also improve aerodynamics and comfort. A wider rim has shown to have better aerodynamics than a narrower rim, and the greater amount of air volume provides additional comfort. Rim widths are measured internal or externally, and while external rim width is important for aerodynamics, we're more concerned with the internal rim width, which, influences comfort, rolling efficiency, and tire shape.

Currently, a narrow road rim measured internally is anything under 15mm, while a wide rim is anything measured internally greater than 17mm. A wider rim will create a wider tire, and so a tire marked as being 25mm, may measure above or below this figure when applied to the wheel. For more on road bike wheels, how they influence ride quality and what to look for, read our guide to Road Bike Wheels.

Tread pattern

Road tires will typically feature a smooth tread surface and are commonly known as ‘slicks’. These offer the highest surface area with the ground on smooth surfaces and provide good levels of rolling resistance and grip. Some road tires do feature a subtle tread pattern, something that could possibly offer marginal improvements in grip, although data on the subject is inconclusive. Other factors like tire pressure, thread count, rubber compounds and rim/tire width are bigger factors when it comes to grip.

A tire's tread is usually made from butyl rubber and can include additives that provide improved puncture protection, improved grip and/or a splash of color. Different types of compounds can be used to improve rolling resistance or traction, and so it's common to see tires with two or even three compounds in the tread to provide enhanced rolling resistance through the middle of the tire, but more grip on the edges.

Puncture protection

Unfortunately for the majority of us, signaling back to the team car and swapping a wheel in the event of a puncture isn't a reality, and so, a tire with good puncture protection is essential.

As mentioned, most tires will have some additional puncture protection either in the form of a sub-tread layer, puncture protection belt or more rubber. These hard wearing compounds prevent sharp objectives like glass, tacks, and thorns from penetrating into the tube and causing a flat. Manufacturer's aim to create an effective puncture protection layer without adding excessive weight or adversely influencing a tire's rolling resistance.

As well as the inbuilt puncture protection mechanisms, there are a few things you can do to prevent punctures.

Inflation: Under-inflated tires are more prone to punctures so keep within the manufacturer's guidelines.

Check for foreign objects: A good habit is to regularly check your tire for any foreign objects that may have embedded themselves along your journey. These small pieces may not cause a puncture immediately, but if you ride with them long enough they will work their way through the tire and into the tube, eventually causing a flat. If the object has created enough of a hole that you can see the fibers of the casing, it's time for a new tire.

Replace worn tires: We discuss below how to check for worn tires, which, is important as worn tires are more prone to punctures. As the tread wears down, there's less preventing foreign objects piercing through and causing a puncture.

Tire pressure

Tyre pressure is a hot topic and in recent times there has been a shift from super high pressure to lower pressure. When the pressure in a tire is 'high', the rolling resistance is improved and the tire is less susceptible to punctures. 'Low' pressure in a tire provides better comfort and grip.

When trying to ascertain the correct tire pressure, it's far more involved than pumping up the tire until it's firm and leaving it there. Factors such as rider weight, tire size, road surface and ride quality will all influence your correct inflation figure.

A general rule is the narrower the tire or the heavier you are, the more pressure will be required. Exactly by how much you need to raise the PSI (pounds per square inch) per kilogram is up for debate but a common relationship is an additional 1% of tire pressure for each 1kg. The below table is from one of the world's leading tire manufacturers, Schwalbe, and provides a good indication of what you should be aiming for.

Body weight

Tire width

approx. 130lbs / 59kg

approx. 185lbs / 84kg

approx. 240lbs / 109kg

25 mm

85 psi

100 psi

115 psi

28 mm

80 psi

95 psi

110 psi

32 mm

65 psi

80 psi

95 psi

37 mm

55 psi

70 psi

80 psi

40 mm

50 psi

65 psi

80 psi

Tire pressure certainly isn't a set and forgot item, you should check your tire pressure often, about once a week as a minimum. Air will slowly filter through the tube and tire and given the high pressure and relatively thin tire walls, this will happen relatively quickly compared to a car tire.

Tire wear

Tires can last anywhere from 1,000km to 10,000km, and so with such a large variance, it's important to know how to check for tire wear and replace when appropriate. Most manufacturers will specify a distance range but depending on the road surface, the overall load, riding conditions and tire pressure, tires may wear prematurely, so use the recommendations as a guide and trust your judgment if you think it's time to change them.

Many tires will have wear indicators in the form of small holes in the center of the tire to indicate the amount of tread left. Once you can no longer see the dots, your tire is well and truly worn. As a rule, if you can see the puncture protection belt or the casing of the tire, it's time for a replacement. If you wanted to be more proactive than that, one of the first signs the tire is wearing is a squaring off of the tire through the center (flat top).

Rolling resistance

Rolling resistant is the resistance from the tires as they contact the road. The major factor affecting rolling resistance is the deformation of the tire as it conforms to the road surface and its small undulations. For a road tire that mostly covers smooth surfaces, higher pressures can be used as there will be small amounts of deformation and resistance as a result. An example where lower pressures are beneficial is on the roads of Paris-Roubaix, where riders have to race across old, cobbled roads. In this scenario, softer tires conform to the surface, meaning the bike has less vertical movement and more forward movement.

All of the factors we've discussed - tire width, pressure, construction, tread pattern - influence a tire's rolling resistance, and so the challenge for manufacturers is to create tire that performs well in each of these areas, or extremely well in one or two specific areas, race tires for example.

Tubes

If you ride a clincher than the choice of tubes can have an impact on ride performance and overall durability. Much like a tire, tubes are predominantly made from butyl rubber and a mixture of other compounds that make them elastic enough so they can be used on a variety of tire sizes, whilst still having thick enough walls to retain air. Tubes can also be made from latex, which, roll better and have higher levels of puncture resistance. The downside of latex tubes is they don't retain air well, and so they need to be inflated regularly, almost daily. As a result, they aren't a popular choice for recreational riders.

Valves are bonded onto tubes in order to be inflated and road tires have two options; Schrader and Presta. Presta valves (aka - high pressure or 'French' valves) are most commonly found on higher-end bikes and are easy to recognize because they are significantly narrower than Schrader valves. Schrader valves are most commonly found on recreational and entry level road bikes, they are also the same valves used on car tires. As each valve is different, unique connections at the pump head are often required to pump up the corresponding tire. Schrader connections require a pin to push down the spring, whereas presta valves are opened via the lock ring. Read our How to Pump Up a Bike Tire article for more information on valve tires.